Generally, it is important that a precision instrument such as a hard-disk-drive case be airtight in order to prevent dust and other foreign matter from penetrating the working parts of the hard-disk drive. Also, because the hard-disk-drive case contains a drive unit that rotates the hard disk at high speed, it is necessary to provide measures for dealing with the heat and vibrations, including noise, that are generated when the drive unit operates. To achieve such objectives, a hard-disk-drive case, which accommodates the hard-disk drive and the drive unit, can be accommodated in an airtight outer enclosure case. From the perspective of heat dissipation, however, an airtight enclosure case generally prevents air circulation and causes heat to build up in the inner hard-disk-drive case. Because in such a situation it is not possible to dissipate the heat sufficiently, there is concern that the performance of the hard-disk drive and the like can be adversely affected by the heat.